Clinical Insights Based in Current Research

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Clinical Insight

Maria Markoulli, PhD, MOptom is part of the academic team at the School of Optometry & Vision Science, University of New South Wales, Australia. She also works in clinical practice and supervises of undergraduate student clinics.

A 34-year-old male polymer chemist had been wearing soft contact lenses uneventfully since the age of 18. His general health was good and he was not taking any medications. He presented for a routine clinical study visit at 8AM at the Brien Holden Vision Institute wearing lotrafilcon A (ALCON, USA) contact lenses on a daily wear schedule and using OptiFree Replenish (ALCON, USA) multipurpose solution. He was asymptomatic and overall satisfied with his contact lens wearing experience.

Presenting visual acuity with contact lenses in situ were Right Eye 6/3.8 and Left Eye 6/4.8.

By virtue of this appearance and the use of a multipurpose solution, this staining was classified as solution-induced corneal staining (SICS) (Figure 1).The participant was advised to continue with contact lens wear but to rinse the contact lenses with saline prior to insertion each morning.

In a subsequent visit, the participant reported mild vision problems and mild symptoms of ocular dryness, and burning and stinging. It was diagnosed with a bilateral asymptomatic infiltrative keratitis (AIK) (Figure 2). He was discontinued from contact lens wear and monitored for one month until resolution. He was then advised to continue contact lens wear using a peroxide-based disinfecting solution and to be reviewed on a three-month basis.

About solution-induced corneal staining (SICS)

SICS is a transient condition characterised by superficial punctate staining associated with the use of multipurpose solutions. It is thought to be due to an incompatibility with particular contact lens-solution combinations, and typically presents as diffuse corneal staining in at least four of the five corneal regions.1 This staining may present evenly across the cornea or in a more annular pattern with greater density in the periphery, and may or may not be associated with symptoms. Diec et al. found that those with SICS had significantly lower comfort than those without.2 These participants also reported worse dryness symptoms at all visits regardless of whether they had presented with SICS. These patients also rated subjective vision as being poorer than those without SICS.2

Typically, SICS is seen more prominently in the early hours of contact lens wear, with more staining evident between one and four hours of lens wear3, 4 and less staining present after six hours of lens wear,4 suggesting that clinical observations should be conducted in the early hours of lens wear in order to detect SICS. The “Institute for Eye Research Matrix Study” found a greater rate of SICS with some contact lens-solution combinations compared to others, with virtually no staining seen when the lens care system was peroxide-based.1

SICS vs. PATH

While it has been suggested that SICS is due to a contact lens-solution incompatibility, recent suggestions are that SICS is in fact preservative-associated transient hyperfluorescence (PATH).5 Bright and colleagues assessed the molecular interactions of disinfectants in multipurpose solutions with the corneal epithelium in vitro. They found that even when used at concentrations 100-fold greater than that in the commercial product, polyhexamethylene biguanide (PHMB) was not destructive to membrane components, suggesting that the staining seen in SICS is benign.5

SICS: Impact on the ocular surface

The field, however, has not been unequivocal regarding the significance of SICS. Choy et al. used flow cytometry to stage early and late necrosis and apoptosis and determine metabolic rate.6 They found that 30% of human corneal epithelial cells displayed early and late necrosis when exposed to Polyquad compared to MPS containing PHMB. Solutions containing the latter caused earlier stage necrosis compared to Polyquad. In addition, the necrotic cells had lost their mitotic activity, indicating a reduced metabolic rate and suggesting that exposure to MPS may lead to a reduced proliferation rate, which may impact the cornea’s ability to recover after damage.6

In a retrospective study conducted by Carnt et al., eyes that experienced SICS were three times more likely to also experience a corneal infiltrative event. The authors suggested that contact lens wearers should be assessed during early hours of lens wear and their lens-solution combination revised should SICS be detected.7 Although the study visits conducted in this study were more frequent than in clinical practice, and hence detection of asymptomatic events was therefore more likely, the authors surmise that without lens wear interruption, both signs and symptoms could be more severe.7 In addition, the suggestion has been made that ensuring appropriate contact lens care could be a preventative strategy for SICS. A study by Peterson and colleagues found that SICS can be significantly reduced by the inclusion of a rub and rinse step before overnight lens disinfection.8

Although the significance of SICS is still being debated, clinicians should aim to monitor for the development of SICS at the appropriate time points and also aim to minimise its occurrence by selecting appropriate lens-solution combinations. Further research is meanwhile warranted to understand the underlying aetiology and significance of SICS.